Add native extensions for the Dart shell to mac and windows

runtime/bin/extensions.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+#include "bin/extensions.h"

[Mads Ager (google), 2012/03/07 14:31:48]

We usually have a blank line after this include before the system includes.

http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Names_and_Orde...

[Bill Hesse, 2012/03/08 12:04:37]

Done.

 #include <stdio.h>
-#include <dlfcn.h>
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/globals.h"
-#include "bin/extensions.h"
 #include "bin/dartutils.h"
 
 Dart_Handle Extensions::LoadExtension(const char* extension_url,
                                       Dart_Handle parent_library) {
-  // TODO(whesse): Consider making loading extensions lazy, so the
-  // dynamic library is loaded only when first native function is called.
-  ASSERT(DartUtils::IsDartExtensionSchemeURL(extension_url));
+  assert(DartUtils::IsDartExtensionSchemeURL(extension_url));

[Mads Ager (google), 2012/03/07 14:31:48]

Please use ASSERT.

[Bill Hesse, 2012/03/08 12:04:37]

Done.

   const char* library_name =
       extension_url + strlen(DartUtils::kDartExtensionScheme);
-  if (strchr(library_name, '/') != NULL) {
+  if (strchr(library_name, '/') != NULL ||
+      strchr(library_name, '\\') != NULL) {
     return Dart_Error("path components not allowed in extension library name");
   }
-  const int buffer_length = strlen(library_name) + strlen("./lib.so") + 1;
-  char* library_path = new char[buffer_length];
-  snprintf(library_path, buffer_length, "./lib%s.so", library_name);
-
-  void* lib_handle = dlopen(library_path, RTLD_LAZY);
-  if (!lib_handle) {
-    delete[] library_path;
+  void* library_handle = LoadExtensionLibrary(library_name);
+  if (!library_handle) {
     return Dart_Error("cannot find extension library");
   }
-  // Reuse library_path buffer for intialization function name.
-  char* library_init_function = library_path;
-  snprintf(library_init_function, buffer_length, "%s_Init", library_name);
+
+  char* init_function_name = MakeString("%s_Init", library_name);

[Mads Ager (google), 2012/03/07 14:31:48]

I think inlining this code here would be just as clear. In particular because
MakeString is very specific about its arguments to the point where the
abstraction doesn't make that much sense?

If we want an abstraction for these, maybe we should provide a StringConcat
function instead that takes an array of char*s and concatenates them?

[Bill Hesse, 2012/03/08 12:04:37]

Did you see all the uses of MakeString in the platform-specific files?

On 2012/03/07 14:31:48, Mads Ager wrote:

   typedef Dart_Handle (*InitFunctionType)(Dart_Handle import_map);
   InitFunctionType fn = reinterpret_cast<InitFunctionType>(
-      dlsym(lib_handle, library_init_function));
-  delete[] library_path;
-  char *error = dlerror();
-  if (error != NULL) {
-    return Dart_Error(error);
+      ResolveSymbol(library_handle, init_function_name));
+  delete[] init_function_name;
+
+  if (fn == NULL) {
+    return Dart_Error("cannot find initialization function in extension");
   }
   return (*fn)(parent_library);
 }
+
+/* Returns a newly allocated string by printing name using format.

[Mads Ager (google), 2012/03/07 14:31:48]

Please use '//' style comments.

[Bill Hesse, 2012/03/08 12:04:37]

Done.

+ * The string must be deleted by the caller. */
+char* Extensions::MakeString(const char* format, const char* name) {
+  const int buffer_length = strlen(name) + strlen(format) + 1;
+  char* new_string = new char[buffer_length];
+  snprintf(new_string, buffer_length, format, name);
+  return new_string;
+}